Enhancing thermal performance and reducing pollutant emissions in a steel reheating furnace through MILD combustion: A study on air distribution and outlet design

This study focuses on the design of inlet air distribution and outlet diameters in an industrial steel reheating furnace, initially configured with a single fuel inlet and four ports for air intake and outlet, aimed at achieving the MILD combustion regime. Further enhancements are implemented to improve the MILD quality, targeting a steel temperature of 1200 degrees C, reducing ingot temperature uniformity to below 30 degrees C, controlling pollutant emissions, and preventing steel oxidation. Hence, the design is optimized through 3D simulations of combustion using the Eddy Dissipation Concept (EDC) model and a conjugate heat transfer process. Results indicate, the steel temperature consistently falls within the target range, with a minimum of 1164 degrees C, attributed to high gas recirculation ratios and an expanded hot zone volume, resulting in ingot temperature uniformity below 25 degrees C. Notably, the configuration with asymmetric inlet air distribution and reduced outlet diameter raises the steel ingot temperature to 1197 degrees C. Additionally, steel oxidation is mitigated by lowering the oxygen concentration around the ingot from 3.72 % to 2.8 %. All configurations maintain the MILD regime, as confirmed by quantitative assessments, with CO and NO emissions recorded below 0.6 ppm and 9 mg/kJ, significantly lower than the EPA standard of 130 ppm and 86 mg/kJ, respectively.